summation?

[comet2000]

Make up five data points and show that ?(X+C) = ?X + NC, where C is any constant (e.g., 4) and N is the number of data points. i don't get it.

 

[mmm4444bot]

Hi Comet:

This might be an exercise intended to check your understanding of Sigma notation and the summation process. But, I dunno.

I'm guessing that they simply want you to show an example ? using actual numbers ? that both sides of the given equation are indeed equal. This will test your understanding of how and what to add up, in order to calculate the values of ?(X+C) and ?X.

The notation might be better written as follows, where a lower-case n is used as the counter and subscript.

\(\displaystyle \sum_{n = 1}^{N} (X_{n} + C) \;=\; \sum_{n = 1}^{N} X_n \;+\; N \cdot C\)

So, when they instruct you to pick five data points, they want you to pick five arbitrary numbers for the set X.

I'll go ahead and do that.

\(\displaystyle X = \{1, 2, 3, 4, 5\}\)

Yes, you can use your example of 4 for C.

The value of N is obvious, right?

Now, it's just a matter of doing the arithmetic on both sides, right?

Your statement of "I don't get it" is too vague for me to determine why you're stuck, or what information you need, or what you already know about this exercise. I'm assuming that you understand Sigma notation and sums (since you didn't ask about ? symbolism) and that you just did'nt get what you're supposed to "pick".

Can you finish?

If not, then what parts don't you get?

As always, if I typed anything that you do not understand, please feel free to ask for an explanation!

Cheers ~ Mark